Sale on 10 products but only with coupon
I need to have a sale on about 10 items for the month of April. The sale price will ONLY be available to customers that have a coupon. The sale should ONLY apply to those items that are on sale.
The only way I can see to make this work is if I had the customer login when they first get to the site. Otherwise, the cart will need to use "discounts" rather than calculations.
Am I missing a technique here?
What can my general approach to this be?
Do you have some specifics on how to do this?